<Matrix-Assisted Laser Desorption/Ionization (MALDI) Mass Spectrometry>
Recently, a soft ionization technique of a biological polymer was established by development of a method of matrix-assisted laser desorption/ionization (MALDI), and a research of proteomics has been rapidly advanced. In the MALDI mass spectrometry, to produce how uniform crystal by using a matrix is one of important factors involved in likelihood of ionization of the molecule to be measured, which greatly contributes to sensitivity, quantitative performance, reproducibility of the analysis. This is particularly important in an automatic analysis.
As for the kind of matrix, those considered to be effective tend to be limited according to the kind of molecule to be measured, the kind of mass spectrometer and the like. For example, in analysis of protein, sinapinic acid, α-cyano-hydroxycinnamic acid and the like are considered as being effective as the matrix. On the other hand, these matrixes are considered as effective, for example, in an analysis of AXIMA-CFRplus (made by SHIMADZU CORPORATION).
On the other hand, an apparatus capable of dispensing a minute amount of a reagent solution is known. Such an apparatus is used usefully for preparing a sample for MALDI mass spectrometry. As an example of such an apparatus, apparatuses disclosed in Japanese Patent Application Laid-Open Publication No. 2003-98154 and Japanese Patent Application Laid-Open Publication No. 2005-283123 may be recited.
<Bioimaging>
In recent years, bioimaging techniques that directly observe cells and biological tissues for visually examining biological phenomena occurring in a living body have been developed and advanced. The bioimaging technique makes it possible to detect a biological molecule while keeping the positional information in the living body. In the bioimaging technique, a thin section of a biological tissue specimen (for example, a frozen section or a paraffin-embedded section) is used as a sample.
Regarding the paraffin-embedded section, today a great number of paraffin-embedded biological tissues used in pathological diagnoses and the like are preserved. The ability of acquiring information of biological molecules from these will allow investigation of diagnosis, therapy, pathologic finding, prognosis and the like in a retrospective manner using past cases, and hence is recognized as being a great advantage in a research of pathology of outbreak of disease, development of a new drug and so on.
As a means in the bioimaging, microscopy is used in most cases, and as other means, mass spectrometry may be used (namely, mass spectrometric imaging).
As an example of mass spectrometric imaging, for example, after subjecting a protein molecule contained in a tissue section to a treatment such as digestion as needed, mass spectrometry is conducted for a plurality of positions on a surface of the tissue section, and an image is formed from mass spectra obtained for respective positions on a surface of the tissue section.
In the mass spectrometric imaging, a frozen section of biological tissue is typically used as a sample. In recent years, for example, Japanese Patent Application Laid-Open Publication No. 2004-347594 reports subjecting a frozen biological tissue section to the MALDI mass spectrometry, and obtaining a MS spectrum. In this art, the matrix solution is microdispensed using inkjet mechanism.
Very recently, there is also reported to execute mass spectrometric imaging by using a paraffin section of a biological tissue. Concretely, 54th ASMS Conference on Mass Spectrometry collected programs, p 147 (Abstract of Session: Imaging MS II Code: ThP18 Time Slot/Poster Number: 333) reports that a paraffin section is subjected to a treatment by a usual immunocytochemical technique, and MALDI mass spectrometric imaging is conducted directly by using reactive matrix.    Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2003-98154    Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2005-283123    Patent Document 3: Japanese Patent Application Laid-Open Publication No. 2004-347594    Non-Patent Document 1: 54th ASMS Conference on Mass Spectrometry collected programs, p 147